Alaska RR SD70M headlights.. and ES44 headlights too! SOLVED!!
Whilst the headlights, number lights and ditch lights can be turned on (F4 HUD or "H" - the rotary switch in the cab doesn't work), there is no beam casting. I do have the appropriate prime mover enhancement from Searchlight Simulations which does mention lighting enhancements, but to no avail. Please note that I'm in the UK, so I'm not sure if any patches for branded SD70Ms (BNSF etc.) would be available or would work. Any suggestions please? Apart from just drive in the daytime LOL! 
Same issue with the ES44 I just discovered tonight.

Same issue with the ES44 I just discovered tonight.

